1. Field
The present disclosure relates to a porous carbonaceous composite material, a positive electrode and a lithium air battery including the carbonaceous composite material, and methods of preparing the same.
2. Description of the Related Art
A lithium air battery generally includes a negative electrode capable of intercalating and deintercalating lithium ions, a positive electrode that oxidizes and reduces oxygen present in the air, and an electrolyte disposed between the negative and positive electrodes.
Since incorporation of oxygen at the positive electrode makes it unnecessary to store air within a positive active material, a lithium air battery may have high capacity. Lithium air batteries have high theoretical energy density, about 3500 watt-hours per kilogram (Wh/kg) or greater, which is about ten times higher than that of lithium ion batteries.
However, because of polarization from a high overvoltage during charging and discharging, existing lithium air batteries have considerably lower energy efficiency than lithium ion batteries.
To lower the charge-discharge overvoltage, various kinds of catalysts have been used; however, the effects thereof have not been sufficient. For example, Li et al. (Yongliang Li et al., Nitrogen-doped carbon nanotubes as cathode for lithium-air batteries, Electrochemistry Communications, 13 (2011) 668-672, the content of which in its entirety is herein incorporated by reference) discloses a lithium air battery including a positive electrode including a carbon nanotube (CNT) doped with nitrogen (N); however, its energy efficiency is also low.
Therefore, there remains a need for materials and methods that further reduce the charge-discharge overvoltage to provide higher charge-discharge energy efficiency.